Sterilizers for medical instruments in the prior art may be large, such as sterilizers used in hospitals, or smaller, such as sterilizers designed for use in a dentist's office and to fit easily on a table. An example of the latter type is that shown in U.S. Pat. No. 5,271,893 (Newman).
The requirements for sterilizing medical instruments are generally prescribed by governing authorities. Thus, the challenge has been to provide an affordable apparatus capable of automatically carrying out the prescribed procedure in the shortest time period. One requirement is that the instrument to be sterilized be subjected to saturated steam at a prescribed temperature for a prescribed period of time. Thus, the interior volume of the sterilizer must be filled with saturated steam, which requires the air in the sterilizer to be replaced with saturated steam as quickly as possible.
The system shown in U.S. Pat. No. 5,271,893 relies on channeling incoming steam to one end of a cassette while allowing air to flow out the other end to purge the air and replace it completely with the steam.